Verifying formulas [closed]

I'm trying to Verify that sin(a + b) = sin(a) cos(b) + sin(b) cos(a) with mathematica, but I don't know how to. I've been given a suggestion to use Simplify, but I don't know where/how.

I just started with Mathematica so forgive me if this has a really simple solution. I've searched around but I haven't found anything.

closed as off-topic by AccidentalFourierTransform, Henrik Schumacher, b3m2a1, xzczd, m_goldbergNov 3 '18 at 17:39

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "This question arises due to a simple mistake such as a trivial syntax error, incorrect capitalization, spelling mistake, or other typographical error and is unlikely to help any future visitors, or else it is easily found in the documentation." – AccidentalFourierTransform, Henrik Schumacher, b3m2a1, xzczd, m_goldberg
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• TrigExpand[Sin[a + b]]. Also FullSimplify[Cos[b] Sin[a] + Cos[a] Sin[b]] – Moo Nov 2 '18 at 16:58
• Thank you so much! – wznd Nov 2 '18 at 17:59

There's a nifty little function called TrigExpand.
Sin[a + b] // TrigExpand